LEFT JOIN in SQL

LEFT JOIN will return all data from the left table. The point:

Even if there are no matching data between Left and Right tables, all data will brought back to the user from LEFT table. That’s the point.

The data that match between two tables plus not-matching data from Left table will be lined in the result.

In the listed results,  if there is no correspond value to in the Right table to the Left table: the returned value will be Null for the Right table.
For an example described in a table:

Buyer	Seller
Michael	Paul
John	Richard
Jonathan	Jools
Sarah	Null
Jack	Null